Electrical inductive apparatus



Aug. 22, 1961 u. A. PEURON ET A1. 2,997,675

ELECTRICAL INDUCTIVE APPARATUS Filed Jan. 25, 1960, Ser. No. 4,289 12 Claims. (Cl. 336S8) This invention relates to electrical inductive apparatus, such as transformers, and more particularly to an improved arrangement for cooling such apparatus.

In order to provide a more compact winding structure in a core and coil assembly for certain types of transformers, such as instrument transformers, solid insulation is often combined in an overall insulation system with a fluid dielectric, such as an insulating oil, which additionally assists in the cooling of such apparatus. As the operating potentials at which transformers of the type `described are employed increase, it may be advantageous to dispose increasing amounts of solid insulation around the windings of such apparatus in order to provide the necessary insulation since the dielectric strength and the specific inductive capacitance of solid insulation are usually greater than those of an insulating fluid, such as an insulating oil. At higher operating potentials, however, the insulating advantages of solid insulation in a transformer of the type described may be offset by the cooling problems created by the presence of the solid insulation around the windings of a transformer. It has been found at higher potentials that the thermally insulating properties of solid insulation disposed around the windings of a transformer may serve to hinder or reduce the cooling eiiiciency of the associated insulating fluid in dissipating or carrying off the heat which results during the operation of a core and coil assembly in a transformer as described.

The heating up of a transformer core and coil assembly of the type described during operation is caused by the presence of several types of losses. As is well known, one type of loss which causes the heating up of a transformer coil assembly in a core and coil assembly is the 12R losses in the conductors included in the windings of the core and coil assembly. One method of reducing the latter type of losses is to increase the cross-sectional area of the conductors employed in the windings of the transformer core and coil assembly, but the reduction in losses by this method is limited by the offsetting increase in eddy current losses as the conductor size is increased. In cer- -tain types of transformers, such as power transformers, the eddy current losses can be conveniently reduced by subdividing the conductors of the windings into parallel connected strands which are transposed to reduce circulating currents. In other types of transformers, such as current transformers, however, it has been found that the latter method of reducing the eddy current losses may not be too practical and additionally may not be too effective because of the diverging magnetic leakage eld produced by the current flow in the high voltage winding of a current transformer.

In transformers designed for higher operating potentials, a second important loss component which produces heating of a transformer core and coil assembly is the dielectric losses in the solid insulation provided around the windings of the core and coil assembly, particularly when the `solid insulation is subjected to a relatively high potential stress or gradient. It is therefore desirable to provide a new and improved transformer construction for use at higher operating potentials which permits the use of solid insulation around the windings of a transformer `core and coil assembly in combination nited States Patent O Patented Ang. 22, i961 ice with a fluid dielectric in an overall insulation system and which at the same time permitsy a compact winding construction that includes an eicient arrangement for dissipating the heat produced by the different losses in a transformer core and coil assembly.

It is an object of this invention to provide a new and improved arrangement for cooling the winding of an electrical apparatus.

Another object of this invention is to provide a new and improved electrical inductive apparatus, such as a transformer, including solid insulation around the wind ing thereof and an improved arrangement for directing an insulating fluid through said winding.

A further object of this invention is to provide a more compact insulation system for the winding of a transformer Which is adapted to dissipate the heat from said winding during operation.

A more specific object of this invention is to provide an improved 'cooling arrangement for a transformer which includes a winding and leads extending therefrom and which employs solid insulation in combination with an insulating fluid in an overall insulating system.

`Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a front elevational view, partly in section, of a transformer constructed in accordance with the teachings of the invention;

FIGUREl 2 is a side elevational View, in partial section, of a portion of the transformer illustrated in FIG.

FIGURE 3 is a diagrammatic representation of the core and coil assembly of the transformer illustrated in FIG. l;

FIGURES 4 and 5 are enlarged front and side elevational views, respectively, of a duct member included in the transformer shown in FIG. l and illustrating the manner in which said duct member is formed;

FIGURE 6 is a side elevational view of the duct member shown in FIGS. 4 and 5 after different portions of said duct member have been folded for assembly with the transformer shown in FIG. 1;

FIGURE 7 is a partial sectional View of the duct member shown in FIG. 6, taken along the line VII- VII in FIG. 6;

FIGURES 8 and 9 are enlarged front and side elevational views, respectively, of an alternative duct construction which may be employed instead of the duct member illustrated in FIGS. 4 through 7;

FIGURE l0 is a perspective View of the duct member shown in FIGS. 8 and 9 after different portions of said duct member have been folded for assembly in a transformer of the type shown in FIG. 1;

FIGURE 1l is a partial front elevational view of the windings of a transformer illustrating a modied form of the invention; and

FIG. 12 is an elevational View of a spacing member employed in the transformer shown in FIG. 1.

Referring now to the drawings and FIGS. l and 3 in particular, there is illustrated a high voltage current transformer 20 constructed in accordance with the teachings of the invention. The transformer 20 includes a core and coil assembly which comprises the primary or high voltage winding 40 and the secondary or low voltage Winding 60 which are both inductively disposed on a suitable magnetic core structure 72, which may be of any conventional type. The core and coil assembly of the transformer 20 may also include an equalizer coil or winding 44 which is also disposed on the magnetic core 72, as described in greater detail in United States Patent 1,932,051. The high Voltage winding 40 includes the iirst and second Winding sections 449A and 40B having the leads 52A and 52B and 54A and 54B, respectively, extending therefrom and electrically connected to the terminals or connectors 77, as best shown in FIG. 1. The terminals 77 may be connected in turn to a high voltage alternating current circuit or line whose current is to be measured or sensed. The high and low voltage windings 4t) and 6G, respectively, are enclosed in a suitable casing or tank 32 while the leads 52A and 52B and 54A and 54B from the first and second high voltage winding sections 40A and 411B, respectively, are enclosed in a suitable tubular insulating bushing or outdoor weather housing 42, as shown in FIG. 1. The casing 32 and the bushing 42 are lled with any suitable tluid dielectric, such as an insulating oil, up to the level indicated at 49. A conventional expansion cap or 'conservator is mounted or disposed at the top of the bushing 42 in order to allow for the expansion and contraction of the dielectric luid provided inside the casing 3.2 and the bushing 42 as the thermal condition of the transformer 20 changes during its operation. An insulating angle ring member 89 may also be disposed at the top of the bushing 42 around the leads 52A, 52B, 54A, 54B adjacent to the point where said leads leave the bushing 42 and enter the expansion cap 48.

The bushing 42 is supported by the cover- 63 of the casing 32 in any suitable manner, such as by a ange member 61 which is rolled on or otherwise secured to the lower end of the bushing 42 and by the llange member 65 which is supported in turn by the cover 63, the flange member 61 being secured to the ilange member 65 by any suitable means, such as bolts or a welded connection, similarly to the construction disclosed in greater detail in United States Patent 2,508,184, which was led May 16, 1950 by M. Morisuye et al. and assigned to the same assignee as the present application.

In particular, the first and second winding sections 40A and 40B of the high voltage Winding 401 are each generally hollow cylindrical or toroidal in configuration and disposed in side-by-side relation with respect to one another or physically parallel to one another on a portion of the magnetic core 72, as best shown in FIGS. l and 2. The low voltage winding 60 is disposed inside the irst and second high voltage Winding sections 40A and 40B in substantially concentric relationship with said high voltage winding sections. The winding sections 40A and 4GB of the high voltage winding 40 each comprises a plurality of spirally wound turns of the conducting strap material 47, which may be substantially rectangular in cross section as illustrated. The irst and second winding sections 40A and 40B of the high voltage winding 4h are spaced apart from one another to define a space or channel 6 therebetween through which the fluid dielectric, whose level is indicated at 49, may ilow or travel as will be further explained hereinafter. ln order to maintain the spacing between the lirst and second winding sections 40A and 40B, respectively, an insulating washer or generally ring-shaped spacing member "62 is disposed between said winding sections and includes a plurality of spacing members 62A which are alternately disposed on the inner and outer periphery of the washer 62 on both sides thereof, as shown in greater detail in FIG. l2, to permit the ow of the lluid dielectric around the washer 62 between the first and second winding sections 40A and 40B, respectively, of the high voltage winding 40.

Since the first and second winding sections 40A and 40B, respectively, of the high voltage winding 4t) are normally connected either in series circuit or parallel circuit relationship with one another to the same high voltage `alternating-current circuit or line, the potential diierence between the turns of each of said winding sections and between said winding sections is relatively low or negligible. For a series circuit arrangement, the lead 4 54A of the winding section 40B may be electrically connected to the lead 52B of the winding section 40A through the terminals 77 while for a parallel circuit arrangement the leads 54A and 54B of the Winding section 4iiB may be electrically connected to the leads 52A and 52B, respectively, ofthe winding section 46A through the terminals 77.

Since the potential diiierence or stress between the high voltage winding sections 46A and 40B is very low or negligible, the potential stress across the space or channel 96 is also very low or negligible. 0n the other hand, the potential difference between the high voltage winding 4i) and the low voltage winding 69 or between the high voltage winding 40 and ground is relatively high. In order to insulate the high voltage winding 40 from the low voltage winding 6&9 and from the grounded Iportions of the transformer Z0, such as the casing 32, the solid insulation 82 is disposed to substantially surround. the high voltage winding il and to provide the necessary insulation between the low voltage winding 60 and the high voltage winding di), as best shown in FIGS. l and 2. The solid insulation S2 may be any suitable insulating material, such as crepe paper in sheet form which is either taped or folded around the high voltage winding 46* and between the high voltage winding 4t) and the low voltage winding 66.

in order to provide an enlarged duct or channel through which the fluid dielectric may flow upwardly or vertically around the leads 52A, 52B, 54A and 54B of the high voltage winding 4%, the tubular shielding member '76, which is formed `from a suitable conducting material, such as brass, is disposed around said leads between the high voltage winding 40 and the upper portion of said leads inside the bushing 42, as best shown in FIG. 1. The upper end of the shielding member 76 is electrically connected to one of the terminals 77 by the conductor 46 so that the shielding member 76 is substantially at the same potential as the high voltage winding 4t?. The lower end of the shielding member 76 opens into the space or channel 96 between the winding sections 40A and 46B of the high voltage winding 40 to permit the flow of a iluid dielectric between said space or channel and the upper end of the shielding member 76. Since the shielding member 76 is at the same potential as the high voltage winding 46, the uid dielectric which flows through said shielding member is substantially free of any potential stress.

in order to substantially eliminate any potential stress in the space or channel 96 between the winding sections @A and 4h13, of the high voltage winding 4U, the shielding member 74 is also provided around the winding sections 4tlA and NBB of the high voltage winding 40. The shielding `member 74 may be formed by winding conducting material, such as copper, in the form of a tape substantially around the outside of the winding sections 40A and 4h?, of the high voltage winding and around the lower end of the shielding member 76 which is then electrically connected to the shielding member 74 so that the shielding member 74 is substantially at the same potential as the shielding member 76 and also at the same potential as the high voltage winding 40. The shielding member 74 may be provided with a gap to prevent a short-circuited turn around the magnetic core 72 and may be spaced away from the turns of the winding sections 40A and 49B by the insulating angle rings 55 and the insulating angle washers 57 at the inner and outer corners, respectively, of said winding sections, as best shown in FIG. 2, to prevent short-circuiting the turns of said winding sections and also to increase the radius of curvature at the corners of said winding sections and thus reduce the potential stress at said corners. A relatively small amount of insulation may also be provided around the turns of the winding sections 40A and 40B to prevent the shielding member '74 from short-circuiting the turns of said winding sections.

In order to insulate the shielding member 76, which is at the same potential as the high voltage winding 40, from the grounded portions of the transformer 20, the layers of solid insulation 8e may be disposed around the shielding member 76 as best shown in FIG. l. The solid insulation 84 may be provided in the form of crepe paper in sheet form which is taped or folded around the shielding member 76 similarly to the solid insulation 82 or the solid insulation S4 may be formed from a plurality of insulating tubular members of various lengths which are concentrically disposed around the shielding member 76.

The space or channel 94 between the outer surface of the solid insulation 84 and the inside of the bushing 42 also serves as a convenient return path for the dielectric fluid after it leaves the upper end of the shielding member 76 and flows back toward the casing 32. In order to reduce the potential stress at the edges of the flange members 61 and 65 and at the edge of the opening 67 in the cover 63 of the casing 32 where the insulating fluid passes adjacent thereto as the insulating fluid returns to the casing 32, a grounded shielding member 98, which is generally cylindrical in configuration and formed from a conducting material, such as copper or aluminum, is disposed around the solid insulation 84 adjacent to the portion o-f said solid insulation 8d which passes through the flange members 61 and 65 and the opening 67 in the cover 63 of the casing 32. The shielding member 98 is electrically connected by the ground strap or conductor 88 to the casing 32 through the flange member 65'. The lower portion of the shielding member 98 rests on or is supported by the supporting members 99, as best shown in FIG. 1.

In order to permit the flow of the liquid dielectric between the outside or outer surface or the solid insulation 82 and the space or channel between the winding sections 40A and 40B of the high voltage winding 40, the channel or duct member 100 is embedded in the solid insulation 82 at the lower portion of the high voltage winding 40 as shown in FIGS. 1 and 2. In general, the duct or channel member 100 which is generally zigzag shaped in configuration extends from the space or channel 96 between the winding sections 48A and 4GB to the outside of the solid insulation 82. The length of the path of iluid flow or travel through the duct or channel member i? is arranged to be greater than the lineal distance between the inner and outer terminal points of said duct member to increase the insulating creepage distance through said duct member and permit a more compact insulating structure around the high voltage winding 40. An additional insulating member 102 formed from a suitable flexible insulating material, such as pressboard, may be also provided on the outside surface of the solid insulation S2 and spaced therefrom by the insulating spacer members 184 to substantially cover the outer opening of the duct or channel member 180 and thus effectively additionally increase the insulating creepage distance through said duct member. When the insulating member 102 is provided, which is curved in shape to follow the outer contour of the solid insulation 82, the fluid dielectric would have to flow between said insulating member and the outer surface of the solid insulation 82 before entering the outer opening of the duct or channel member 100.

Referring to FIGS. l through 7, the duct or channel member 100 is preferably formed from a suitable, flexible insulating material, such as press-board. In particular, the duct member 108 is formed from a plurality of sections of insulating material 112 and a plurality of side wall or spacing insulating members 114. Each pair of the side walls or spacing members 114 is arranged in spaced relationship substantially parallel to the axis of the unfolded duct or channel member lili), as best shown in FIG. 4. Each pair of the side wall or spacing members 114 is separated longitudinally of the axis of the unfolded duct member 100 from the adjacent pairs of said spacing members by a space or distance indicated at 124 in FIG. 4. The length of each of the sections 112 is selected or arranged to substantially bridge or span two successive pairs of the spacing or side wall members iii-fi# and the space 124 therebetween with the successive sections 112 which make up the duct member let) being bonded or cemented to alternate sides of the side wall or spacing members 114, as best shown in FIG. 5. The first and second generally rF-shaped insulating end sections or tab members are provided at the inner and outer ends, respectively, of the duct member 18d for securing said duct member either to the high Voltage winding 40 or to the solid insulation 82 during the assembly of the duct member 10G with the solid insulation 82' around the high voltage winding 48. Referring to FIGS. 6 and 7, after the unfolded duct member 100 is folded to forfm a generally zig-zag shaped duct member, the cross-sectional area of the iiuid flow path through said duct member is substantially rectangular as indicated at 122 in FIG. 7. Since the duct member 168 is folded in alternate opposite directions at the spaces 124, a continuous fluid ow path remains around the corners of the duct member 198 between each curved bend in the sections 112 and the meeting edges of the sections 112 on the opposite sides of the spacing or side wall members 114i, as best shown in FIG. 6. The balance of the duct walls at the folded corners of the duct member is provided by the solid insulation 82 which is packed, folded or taped around said duct member when it is assembled with the high voltage winding itl of the transformer 20.

Considering the overall operation of the cooling arrangement provided in the transformer Ztl as described, the closed path of tlow or travel of the fluid dielectric inside the casing 32 and the bushing i2 may be traced starting from a point inside the casing 32 below the insulating member 102. The fluid dielectric enters the space between the insulating member 1%2 and the outer surface of the solid insulation 82 at both sides of said insulating member and flows towards the outer opening of the duct member 10i). The fluid dielectric then flows through the duct or channel member 10i? and flows from the inner end of said duct member into the space or channel 96 between the winding sections 40A and 40B of the high voltage winding 49, the length of the uid ow path through the duct member 100 being greater than the lineal distance between the terminal points thereof, as previously mentioned. The fluid dielectric next flows or travels in parallel paths within the solid insulation 82 between the winding sections 46A and 40B of the high voltage winding 4t), through the channel or duct 96 therebetween to the lower end of the shielding member 76 which opens into the channel 96. The fluid dielectric then fiows or travels in an upward direction through the tubular shielding member 76 around the leads 52A, 52B, 51M and 54B of the high voltage winding 4? and leaves the shielding member 76 at the upper end thereof in the space between said shielding member and the inside of the bushing 42, as previously described. The iluid dielectric which has been heated by this time by its contact with the solid insulation 82 and the high voltage winding 48 during the operation of the transformer 20 next hows in a downward direction in the space between the inside of the bushing 42 and the outer surface of the solid insulation 84 which is provided around the shielding member 76, said fluid dielectric passing back into the casing 32 through the space between the grounded shielding member 98 and the ange members 61 and 65 and through the opening 67 in the cover 63 of the casing 32'. Finally, the fluid dielectric ows back down around the insulating member 102 and the solid insulation 52 to the assumed starting point of its travel to thereby complete a closed loop through the core and coil assembly of the transformer Ztl.

It is important to note that the closed loop in which the fluid dielectric inside the transformer 2G travels is arranged to be through zones or areas of either very low or negligible potential stress, as previously described, while the fluid dielectric is carrying 'off the heat produced by the different losses in the high voltage winding ill and the heating produced by the dielectric losses in the solid insulation g2 which is required for operation at higher.

operating potentials. rhe latter feature is of particular importance since the dielectric strength of a fluid dielectric is usually less than that of the solid insulation S2 and since it is well known that an insulating material takes up potential stress in substantially inverse ratio to its specific inductive capacitance. The construction disclosedtherefore substantially eliminates the possibility of an insulation failure in the fluid dielectric provided while permitting a more compact winding and insulation structure in which the heating produced by the different losses is eiiiciently dissipated.

In particular, it should be noted that the potential stress inside the shielding member 76 is substantially negligible since it is electrically connected to the high voltage winding 4l) as previously described while the potential Stress between the winding sections 40A and QB of the high voltage Winding eil is also substantially negligible because of the shielding member 74 which is provided around said high voltage winding sections as previously described. In addition, the potential streuss in the duct member ltll is reduced to a very low value by arranging the fluid flow path therethrough to be greater than the lineal distance between the terminal points thereof as previously described, While the fluid flow path between the solid insulation 84 and the inside of the bushing 42 is also arranged to be through a very low potential stress portion of the transformer Ztl. Finally, the potential stress in the lluid iow path between the lower end of the outside surface of the solid insulation 84 and the edges of the flange members 6l and 65 and the opening 67 on the cover of the bushing 32 is reduced to substantially a negligible value by providing the grounded shielding member 98 as previously described.

Referring now to FIGS. 8 through l0, there is illustrated a duct member 200 which may be substituted as an alternative construction for the duct member 101i previously described. In general, the duct member 26? is generally Zig-zag shaped similarly to the duct member 160 except that the cross-sectional area of the duct provided by the duct member 260 is substantially triangular in shape rather than being substantially rectangular in shape as is the cross-sectional area of the duct member 100.

In particular, the duct member 260 is formed from a substantially continuous, flexible insulating material 212, such as pressboard, having a plurality of generally V- shaped notches or recesses 21S substantially equally spaced from one another on opposite sides of the insulating material 212, as best shown in FIG. 8. A plurality of spacing or side wall members 214 are bonded or cemented to one side of the insulating material 212 with a pair of said spacing members provided between each successive pair of V-shaped recesses 218 on the same side of the insulating material 23.2 and with each pair of the spacing members 214 separated by a space or distance indicated at 219 in FIG. 8. The insulating material 2l2 is next folded on its central axis, as indicated at 213, to provide a duct member having a substantially triangular shaped cross-sectional area, as indicated at 223 in FIG. 1G. Finally, the duct member 26? is folded at the V-shaped recesses 21? in opposite directions for successive alternate recesses to form a generally zig-zag shaped duct member 2li@ as best shown in FIG. l0 which is then assembled with the solid insulation around the high voltage winding of the associated transformer similarly to the duct member llltl which is assembled with the solid insulation 2 around the high Voltage Winding 40. Solid insulation similarly to the solid insulation 82 could be employed to complete the duct walls of the duct member 2li@ when assembled with the associated transformer. The duct member 200 permits the use of a continuous sheet of insulating material rather than a plurality of sections of insulating material, as in the duct member lill) previously described.

Referring now to FIG. ll, there is illustrated a modilied form of the invention in a transformer 300 which includes a high voltage winding 320 and a low voltage winding 330 as well as a plurality of duct members 310 which may be of the types previously described. The high voltage winding 326 of the transformer 300 includes a plurality .of high voltage winding sections which are electrically connected in circuit ralationship similarly to the winding sections 4M; and `40B of the transformer 2Q. rhe potential difference between the adjacent Winding sections of the high voltage winding 320 is either very low or negligible, such that a plurality of duct members Sill may permit the flow of a uid dielectric from the outside of the solid insulation 382 which surrounds the high voltage windmg 320 to the spaces or channels between dierent pairs of adjacent high voltage winding ses-`U "lere required in :i particular application, such as in an instrument transformer, and more particularly, in a potential transformer.

-lt is to be noted that in a transformer such as the transformer 2i) shown in FIGS. l and 2, that the vertical uid ow path which includes the duct member 100, the space or channel 96 between the high voltage winding sections 46A and liiB and the tubular shielding member 76 provides a chimney effect in forcing the fluid dielectric to new through the path previously described when the core and coil assembly of the transformer 20 heats up during operation and provides a thermal head in the fluid path.

lt is to be understood that the construction disclosed may be adapted to any type of electrical inductive apparatus, such as a transformer, in which the quantity of solid insulation required to be provided around the high voltage windings thereof for a particular operating potential creates a thermal barrier to the dissipation of the heat which results in said windings during the operation thereof and in which it is desirable to provide a compact winding and insulation structure with more eflicient cooling thereof. It is also to be understood that other configurations may be substituted for the generally zig-zag shape of the duct members 10i) and 2li@ in a particular application in order to provide `a fluid flow path which is longer or greater than the lineal distance between the terminal points of the duct member, such as a duct member which provides -a generally helical fluid ow path through associated solid insulation.

The apparatus embodying the teachings of this invention has several advantages. For example, the construction disclosed provides a more compact winding and insul ation structure for the high voltage windings of an electrical inductive apparatus, such as a transformer, in which a fluid dielectric is combined with solid insulation in an overall insulation system while still providing a more efficient cooling arrangement for dissipatiug the heat which arises in the windings in the solid insulation of such apparatus during the operation thereof. In addition, the possibility of an insulation failure in the fluid dielectric of an electrical inductive apparatus as disclosed is substantially eliminated =by subjecting said liuid dielectric to a potential stress which is either very low or negligible.

Since numerous changes may be made in the abovedescribed apparatus and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the -accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. In a transformer, the combination comprising, a

magnetic core, a winding having a plurality of winding sections disposed on said core and spaced apart from one another, said winding sections being connected in circuit relation with the potential diierence between adjacent winding sections being substantially negligible, solid i11- sulation disposed to substantially surround said winding, an insulating iiuid surrounding said core and winding, and a duct extending from the outside of said solid insulation to the space between an adjacent pair of said winding sections to permit the iiow of said iluid therebetween, the length of the path of duid ilow through said duct being greater than the lineal distance between the terminal points of said duct to increase the insulating creepage distance through said duct.

2. In a transformer, the combination comprising, a magnetic core, a winding having a plurality o-f winding sections disposed on said core and spaced apart from one another, said winding sections being connected in circuit relation with the potential difference between adjacent winding sections being substantially negligible, solid insulation disposed to substantially surround said winding, an insulating uid surrounding said core and winding, a duct extending from the outside of said solid insulation `to the space between an adjacent pair of said winding sections to permit the flow of said fluid therebetween, the length of the path of iluid ow through said duct being greater than the lineal distance between the terminal points of said duct to increase the insulating creepage distance through said duct, and an insulating member disposed on the outside of said solid insulation and spaced therefrom to substantially cover the outer end of said duct and increase the eiective insulating creepage distance af said duct.

3. In a transformer, the combination comprising a magnetic core, a winding having a plurality of winding sections disposed on said core and spaced apart from one another, said winding sections having leads connected in :ircuit relation with the potential difference between adiacent winding sections being substantially negligible, ;olid insulation disposed to substantially surround said winding, an insulating iluid surrounding said core and winding, a duct extending from the outside o-f said solid insulation to the space between :an adjacent pair of said winding sections to permit the ow of said iluid therenetween, the length of the path of fluid ilow through said duct being greater than the lineal distance between the erminal points of said duct to increase the insulating :reepage distance through said duct, and a tubular shieldng member disposed `around said leads and having one and open to the space between an adjacent pair of said winding sections to permit the ow of said uid there- Jetwcen.

4. In a transformer, the combination comprising, a nagnetic core, a winding having a plurality of winding sections disposed on said core and spaced apart from one another, said winding sections having leads connected in circuit relation with the potential difference be- `:ween adjacent winding sections being substantially negligible, solid insulation disposed to substantially surround said winding, an insulating fluid surrounding said core and winding, a duct extending from the outside of said solid insulation to the space between an adjacent pair 3f said winding sections to permit the ilow of said iluid ;herebetween, the length of the path of fluid flow through said duct being greater than the lineal distance between he terminal points of said duct to increase the insulating :reepage distance through said duct, and a tubular shieldng member disposed around said leads having one end )pen to the space between an adjacent pair of said windng sections to permit the ow of said fluid therebetween.

5. In a transformer, the combination comprising a nagnetic core, a winding having a plurality of winding iections disposed in side-by-side relation and spaced apart me from another on a portion of said core, said winding sections being connected in circuit relation with one another, the potential difference between said adjacent winding sections during operation being negligible, solid insulation disposed to substantially surround said winding, a fluid dielectric, said winding and solid insulation being substantially immersed in said fluid dielectric, and a generally Zig-zag shaped duct member formed from insulating material, said duct member being arranged to extend from the outer surface of said solid insulation to the space between adjacent winding sections to permit the ow of said fluid dielectric from outside said solid insulation through the space between the adjacent winding sections while providing substantially a predetermined insulating creepage distance through said duct member.

6. In a transformer, the combination comprising a magnetic core, a winding having a plurality of winding sections disposed in side-by-side relation and spaced apart one from another on a portion of said core, said Winding sections being connected in circuit relation with one another, the potential difference between said adjacent winding sections during operation being negligible, solid insulation disposed to substantially surround said winding, a iluid dielectric, said winding and solid insulation being substantially immersed in said fluid delectric, a generally Zig-zag shaped duct member formed from insulating material, said lduct member being arranged to extend from the outer surface of said solid insulation to the space between adjacent winding sections to permit the iiow of said fluid dielectric from outside said solid insulation through the space between the adjacent winding sections while providing substantially a predetermined insulating creepage distance through said duct member and an insulating member disposed on the outside of said solid insulation and spaced therefrom to substantially cover the outer end of said duct member.

7. In a transformer, the combination comprising a magnetic core, a winding having a plurality of winding sections disposed in side-by-side relation and spaced apart one from another on a portion of said core, said winding sections being provided with leads connected in circuit relation with one another, the potential difference between said adjacent winding sections during operation being negligible, solid insulation disposed to substantially surround said winding, a fluid dielectric, said lwinding and solid insulation being substantially immersed in said fluid dielectric, a generally zig-zag shaped duct member formed from insulating material, said duct member being arranged to extend from the outer surface of said solid insulation to the space between adjacent winding sections to permit the flow of said fluid dielectric from outside said solid insulation to the space between the adjacent winding sections while providing substantially a predetermined insulating creepage distance through said duct member and a tubular shielding member disposed around the leads and having one end adjacent to the space between adjacent windings to permit the ow of said uid dielectric therebetween.

8. In an instrument transformer, the combination comprising a high voltage winding including a plurality of winding sections spaced apart from one another and connected in circuit relation with one another, the potential difference between adjacent winding sections during 0peration being substantially negligible, solid insulation substantially surrounding said winding, insulating uid surrounding said winding, and at least one generally Zigzag shaped duct member extending from the outside of said solid insulation to the space between adjacent winding sections to permit the ilow of said insulating fluid therethrough while maintaining the insulating creepage ydistance through said duct above substantially a predetermined value.

9. In an instrument transformer, the combination comprising a high voltage winding including a plurality of winding sections spaced apart from one another and connected in circuit relation with one another, the potential difference between adjacent winding sections during operation being substantially negligible, solid insulation substantially surrounding said winding, insulating uid surrounding said winding, at least one generally zig-zag shaped duct member extending from the outside of said solid insulation to the space between adjacent Winding sections to permit the flow of said insulating fluid therethrough while maintaining the insulating creepage distance through said duct above substantially a predetermined value, and an insulating member disposed on the outside of said solid insulation and spaced therefrom to cover the outer end of said duct member and to increase the eiective insulating creepage distance.

l0. In an instrument transformer, the combination comprising a high voltage winding including a plurality of winding sections spaced apart from one another and having leads connected in circuit relation with one another, the potential dii-ference between adjacent winding sections during operation being substantially negligible, solid insulation substantially surrounding said winding, insulating fluid surrounding said winding at least one generally zigzag shaped duct member extending from the outside of said solid insulation to the space between adjacent winding sections to permit the flow of said insulating fluid therethrough while maintaining the insulating creepage distance through said duct above substantially a predetermined value, a tubular shielding member formed from conducting materialv and having one end opening into the space between adjacent winding sections to permit the ow of insulating fluid therebetween.

1l. In a current transformer, the combination cornprising, a magnetic core, a high voltage winding including two generally cylindrical winding sections disposed in side-by-side relation on said core Iand spaced apart from one another, said winding sections being connected in circuit relation with the potential difference between said winding sections during operation being substantially negligible, solid insulation disposed to substantially surround said winding, an insulating fluid surrounding said core and winding, and a generally Zig-zag shaped duct member formed from insulating material and extending from the space between said winding section to the outside of said solid insulation to permit the ow of said insulating uid therebetween while providing an insulating creepage distance therethrough above substantially a predetermined value.

l2. In a current transformer, the combination comprising, a magnetic core, a high voltage winding including two generally cylindrical winding sections disposed in side-by-side relation on said core and spaced apart from one another, said winding sections being connected in circuit relation with the potential difference between said winding sections during operation being substantially negligible, solid insulation disposed to substantially surround said winding, an insulating fluid surrounding said core and winding, a generally zig-zag shaped duct member formed from insulating material and extending from the space between said winding sections to the outside of said solid insulation to permit the ow of said insulating uid therebetween while providing an insulating creepage distance therethrough above substantially a predetermined value, and an insulating member disposed on the outside of said solid insulation and yspaced therefrom to substantially cover the outer end of said duet member and increase the effective insulating creepage distance through said duct member.

No references cited. 

